Stock material or miscellaneous articles – Hollow or container type article – Paper containing
Reexamination Certificate
2000-12-07
2002-08-20
Niland, Patrick D. (Department: 1714)
Stock material or miscellaneous articles
Hollow or container type article
Paper containing
C428S035200, C428S035700, C428S523000, C525S088000, C525S095000, C525S098000, C525S232000, C525S240000
Reexamination Certificate
active
06436494
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a polypropylene resin composition and to a non-stretched film made of such resin composition. Specifically, the invention relates to a polypropylene resin composition comprising a polypropylene resin, a specific ethylene/&agr;-olefin random copolymer and a specific propylene/ethylene/1-butene random copolymer, as well as to a non-stretched film made of such resin composition.
BACKGROUND OF THE INVENTION
Films of polypropylene resins have, due to their favorable performances in the mechanical properties, such as tensile strength, stiffness and so on, in the optical properties, such as gloss, transparency and the like and in the hygienic acceptability as the material for dealing with food products by, such as, non-toxicity and odorless property, found their wide uses in the field of packaging of food products.
It has been practised here to incorporate in the resin a rubbery component, such as an ethylene/propylene copolymer, ethylene/butene copolymer or the like, since a film made solely of a polypropylene resin exhibits an inferior impact resistance and permits to effect heat sealing only at higher temperatures.
While an addition of a rubbery component may improve the impact resistance and may permit to lower the heat-sealing temperature, it is accompanied by a shortcoming that the transparency of the resulting film will be deteriorated and the strength of heat sealing becomes decreased.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a polypropylene resin composition for non-stretched film capable of bringing about a non-stretched film superior in the transparency, in the impact resistance, in the low temperature heat-sealability and in the strength of heat-sealing.
Another object of the present invention is to provide a non-stretched film superior in the transparency, in the impact resistance, in the low temperature heat-sealability and in the strength of heat-sealing.
The present invention provides for a polypropylene resin composition for non-stretched film as well as for a non-stretched film given below:
(1) A polypropylene resin composition for non-stretched film, comprising
(A) 50-95 parts by weight of a polypropylene resin,
(B) 3-40 parts by weight of an ethylene/&agr;-olefin random copolymer with the &agr;-olefin having at least three carbon atoms, the said random copolymer having a content of the structural unit of ethylene of 60-95 mole %, a density of 0.900 g/cm
3
or lower, an MFR (melt flow rate, determined according to ASTM D-1238 at 190° C. under a load of 2.16 kg) of 0.1-50 g/10 min. and a molecular weight distribution expressed by Mw/Mn, determined by gel permeation chromatography(GPC), of 3 or less, and
(C) 2-20 parts by weight of a propylene/ethylene/1-butene random copolymer, which meets the three conditions 1), 2) and 3) given below,
wherein the amounts of (A), (B) and (C) sum up to 100 parts by weight and wherein the said random copolymer (C) meets the following three conditions, namely,
condition 1) that it comprises 50-88 mole % of propylene unit, 2-30 mole % of ethylene unit and 10-40 mole % of 1-butene unit and that the content of 1-butene unit is greater than the content of ethylene unit;
condition 2) that it has an MFR, determined according to ASTM D-1238 at 230° C. under a load of 2.16 kg, of 0.1-50 g/10 min.; and
condition 3) that it has a molecular weight distribution expressed by Mw/Mn, determined by gel permeation chromatography (GPC), of 3 or less.
(2) A polypropylene resin composition for non-stretched film as defined in the above (1), wherein the polypropylene resin (A) comprises at least one selected from the group consisting of propylene homopolymers, propylene/&agr;-olefin random copolymers having a content of the &agr;-olefin other than propylene of 10 mole % or lower and propylene/&agr;-olefin block-copolymers having a content of n-decane-extractable portion of 10% by weight or less.
(3) A polypropylene resin composition for non-stretched film as defined in the above (1) or (2), wherein the ethylene/&agr;-olefin random copolymer (B) is an ethylene/butene random copolymer having an ethylene unit content of 60-95 mole % and a 1-butene unit content of 5-40 mole %.
(4) A non-stretched film made of a polypropylene resin composition as defined in either one of the above (1) to (3).
DETAILED DESCRIPTION OF THE INVENTION
Below, the polypropylene resin composition for non-stretched film and the non-stretched film according to the present invention will be described in detail.
The polypropylene resin composition for non-stretched film according to the present invention comprises a polypropylene resin (A), an ethylene/&agr;-olefin random copolymer (B) and a propylene/ethylene/1-butene random copolymer (C).
The non-stretched film according to the present invention is made of the above polypropylene resin composition.
First, the description is directed to the polypropylene resin (A) composing the polypropylene resin composition.
According to the present invention, any voluntary one among known polypropylene resins can be chosen for the polypropylene resin (A). For such a polypropylene resin (A), there may be enumerated, for example, homopolymers of propylene and random copolymers and block-copolymers of propylene/&agr;-olefin with the &agr;-olefin being other than propylene. The polypropylene resin (A) may be modified with a monomer having polar group(s), such as maleic anhydride or so on.
Favorable polypropylene resins (A) comprises at least one selected from the group consisting of homopolymers of propylene, propylene/&agr;-olefin random copolymers containing at the most 10 mole %, preferably 8 mole % or less, of other &agr;-olefin unit and propylene/&agr;-olefin block-copolymer having a content of n-decane-extractable portion, namely, a portion to be extracted by n-decane, of 10% by weight or less, especially 8% by weight or less.
In the context of this specification, it is meant by the “&agr;-olefin unit” a structural unit derived from an &agr;-olefin in a polymer. The same applies also to the “ethylene unit”, “propylene unit” and “1-butene unit”. In the present invention, &agr;-olefin encompasses ethylene.
As the &agr;-olefins composing the propylene/&agr;-olefin random copolymer or the propylene/&agr;-olefin block-copolymer, there may favorably be enumerated &agr;-olefins having 2-20 carbon atoms other than propylene and concrete examples thereof include ethylene, 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-decene, 1-dodecene, 1-hexadecene and 4-methyl-1-pentene. These &agr;-olefins may be incorporated either solely or in a combination of two or more of them.
The polypropylene resin (A) to be employed according to the present invention can be produced by processes known per se using a solid titanium catalyst or a metallocene catalyst known per se.
It is favorable that the polypropylene resin (A) has a degree of crystallinity, determined by X-ray diffraction method, of at least 40%, especially at least 50%, and a melting point (Tm), determined by DSC method, in the range of 100-165 ° C. It is preferable to incorporate a polypropylene resin (A) having a melting point higher than that of the ethylene/&agr;-olefin random copolymer (B) and that of the propylene/ethylene/1-butene random copolymer (C).
The polypropylene resin (A) has a melt flow rate (MFR), determined in accordance with ASTM D 1238 at 230° C. under a load of 2.16 kg, in the range of, usually, 0.1-300 g/10 min., preferably 1-50 g/10 min.
The polypropylene resin (A) may be incorporated either alone or in a combination of two or more.
Now, the ethylene/&agr;-olefin random copolymer (B) will be described.
The ethylene/&agr;-olefin random copolymer (B) has characteristic features of
1) a content of the ethylene unit in the range of 60-95 mole %, preferably 70-90 mole %,
2) a density of 0.900 g/cm
3
or less, preferably in the range of 0.850-0.880 g/cm
3
,
3) an MFR (melt flow rate, determined according to ASTM D 1238 at 190° C. under a load of 2.16 kg) in the range of 0.1-50 g/10 min., preferably
Nakagawa Norihiko
Tanaka Yasuo
Yasaka Naoto
Mitsui Chemicals Inc
Niland Patrick D.
Sherman & Shalloway
LandOfFree
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